1. Technical Field
The present disclosure relates to a bearing mechanism suitable as a structure of a bearing, such as a mechanical tool bearing, being subjected to high load at low rotational speeds and low load at high rotational speeds.
2. Related Art
Generally, in the case of using a ball bearing as a bearing for a high-speed rotating shaft, the accuracy of rotation can be improved by increasing the stiffness of the rotating shaft in the radial and axial directions. Hence, the ball bearing is preloaded. In the preloading, one of the inner and outer rings of the ball bearing is fixed, and pressure is axially applied to the other. Pressure is therefore applied (held) beforehand to between the inner and outer rings. Methods for applying preload include, for example, the fixed position preload method and the constant pressure preload method. In the fixed position preload method, as illustrated in FIG. 13, in terms of adjacent bearings 110 and 110, outer rings 111 and 111 are brought into contact with each other, and a space s is defined between inner rings 112 and 112. In this state, pressure is applied to these inner rings 112 and 112 from both sides in the axial direction. In the constant pressure preload method, as illustrated in FIG. 14, a spring 213 is provided between outer rings 211 and 211 of adjacent bearings 210 and 210. The outer rings 211 and 211 are biased by the spring 213.